1. Field of the Invention
The present invention relates to a sealing mechanism for container opening having a combination of a cylindrical opening formed on a container body and a cap for sealing the cylindrical opening.
2. Description of the Related Art
A container provided with: a cylindrical opening acting as an outlet (a pouring opening) for the content; and a cap for sealing the cylindrical opening is widely used as a container for liquid beverage, fluid food, seasonings and so on. In such a container of a type that the opening is sealed only by an engagement between the cap and the cylindrical opening, there are concerns that the content may leak out of the container due to a defective molding or flaw at the engagement portion. Furthermore, in the case that the container in which the content is filled and sealed is subjected to a retort treatment which is a sterilization by heating to a high temperature, there is a risk that the content may leak out, due to a pressure rising in the container during the retort treatment. Furthermore, if there is difference of shrinkage or expansion ratio between the cap and the cylindrical opening in the retort treatment, the sealing of the opening may become insufficient, resulting in the leakage of the content.
Conventionally, in order to improve the sealing performance of the container having such a cylindrical opening, the opening is sealed by using an inner sealing element capable of adhering to the opening. However, in order to take the content out of the container sealed with the inner sealing element, the cap needs to be opened firstly, and then the inner sealing element adhering to the opening needs to be peeled off from the opening. It is bothersome.
In view of the above concerns or problems, there is proposed a container which allows an inner sealing element to be peeled off from the opening at the same time when the cap is opened. For example, Japanese examined Utility Model Application Publication No. S49-26614 and Japanese Patent Application Laid-Open No. 2004-83080 describe a sealing device in which an inner sealing element adheres to both the lip of the opening and the inside surface of the cap in such a manner that an adhesion force between the inner sealing element and the inside surface of the cap is greater than an adhesion force between the inner sealing element and the lip of the opening. Thereby, when the cap is opened, the inner sealing element can be peeled off automatically from the lip of the opening, while the adhesion between the inner sealing element and the inside of the cap is maintained.